JP2008081811A - Method for producing aluminum foil for electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent, when annealing aluminum foil for electrolytic capacitor, the occurrence of nonuniformity of oxide film in a coil-width direction, oxidation phenomena at edges, etc., and the resultant occurrence of inferior etching in the subsequent step. <P>SOLUTION: When annealing aluminum foil produced by cold rolling, the atmosphere is made to a negative-pressure atmosphere and also a pressure decrease by discharge of atmospheric gas and a pressure increase by introduction of atmospheric gas are repeated in a pressure range from 0.4×10<SP>5</SP>to 0.9×10<SP>5</SP>Pa. It is desirable to set the ultimate pressure of pressure decrease and the ultimate pressure of pressure increase at 0.4×10<SP>5</SP>to 0.6×10<SP>5</SP>Pa and 0.7×10<SP>5</SP>to 0.9×10<SP>5</SP>Pa, respectively. By this method, an oxide film having high uniformity in a coil-width direction can be formed on the surface of aluminum foil in coil form without causing winding deviation etc. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing an aluminum foil for electrolytic capacitors used for electrodes of electrolytic capacitors.

As an electrode of an aluminum electrolytic capacitor, a high-purity aluminum foil having a thickness of 20 to 150 μm and etching in a strong acid solution to expand the surface area is generally used.
The aluminum foil is made into a foil having a predetermined thickness through cold rolling using a high-purity aluminum material as a raw material, and then roughened by the etching. Of these aluminum foils, foils used for medium- and high-voltage electrolytic capacitors are thinned by the above-described aluminum foil rolling, wound into a coil, and accommodated in a batch furnace, at a high temperature of 500 ° C. or higher. Etching is improved by annealing and increasing the cubic ratio to 95% or more.

In the annealing, an oxide film grows on the surface of the aluminum foil by heating at a high temperature. However, when this oxide film grows excessively, the etching property is remarkably lowered. Therefore, the thickness of the oxide film is usually controlled to 20 to 80 mm during annealing. For this purpose, it is common to manage the oxygen concentration or dew point in the annealing atmosphere. For example, after evacuating the annealing furnace before annealing, an inert gas such as Ar or N _{2 is} introduced to reduce the oxygen concentration in the furnace, and then the aluminum foil is heat-treated. However, the rolling oil, moisture, etc. are attached to the surface of the aluminum foil after the foil rolling, and during the annealing, the heated rolling oil and moisture are gasified, contaminating the annealing atmosphere, and gasified substances are present. When extruded from the center of the coil to the end, it reacts on the surface of the aluminum foil, causing problems such as variations in the oxide film and oxidation of the end. Variation in the oxide film causes variation in the capacitance of the electrolytic capacitor. In addition, the excessively oxidized end portion has poor etching property and cannot be roughened.

In order to prevent such variations in the oxide film, for example, the aluminum foil is degreased to remove the rolling oil by cleaning the surface, and further, 350 to 450 ° C. in an atmosphere of 500 to 950 Torr. And then temporarily reducing the pressure to 1 Torr or less to generate moisture from each layer of the coil, discharging it to the outside of the furnace at the time of the pressure reduction, and then annealing again to 450 to 600 ° C. at 500 to 950 Torr. And a manufacturing method (see Patent Document 1) intended to form a uniform oxide film.
Japanese Patent Laid-Open No. 10-152766

  However, in the proposed technique, when the pressure is once reduced to 1 Torr or less, the gas remaining inside the coil is suddenly exhausted, so that the coil is unwound or the aluminum foils are in close contact with each other. There is. The adhesion between the aluminum foils causes wrinkles when the coil is rewound in a later process.

  The present invention has been made against the background of the above circumstances, and is an aluminum for electrolytic capacitors that can form a highly uniform oxide film in the coil width direction on the surface of the coiled aluminum foil without causing a winding slip or the like. It aims at providing the manufacturing method of foil.

That is, among the methods for producing an aluminum foil for electrolytic capacitors according to the present invention, the invention according to claim 1 has a negative pressure atmosphere when annealing the aluminum foil produced by cold rolling, and 0.4 × in 10 ⁵ Pa~0.9 × 10 ⁵ pressure range ^Pa, and performing the annealing by repeating the step-up by introduction of the step-down and the ambient gas by the discharge of the atmospheric gas.

Invention of a manufacturing method according to claim 2 electrolytic aluminum foil capacitor as claimed in the invention of claim 1, wherein, in the ultimate pressure of the step-down in the range of ^{0.4 × 10 5 Pa~0.6 × 10 5} Pa is set, ultimate pressure of the booster is characterized in that it is in the range of ^{0.7 × 10 5 Pa~0.9 × 10 5} Pa.

  The invention of the method for producing an aluminum foil for electrolytic capacitors according to claim 3 is the invention according to claim 1 or 2, wherein one cycle in which the step-down and the step-up are performed is within 30 minutes.

The invention of the method for producing an aluminum foil for electrolytic capacitors according to claim 4 is the invention according to any one of claims 1 to 3, wherein the aluminum foil is heated when the aluminum foil is heated and annealed at an annealing temperature. There and sets the ambient pressure in the middle heated without reaching 300 ° C. to ^{0.8 × 10 5 Pa~0.9 × 10 5} Pa.

  The invention of the method for producing an aluminum foil for electrolytic capacitors according to claim 5 is the invention according to any one of claims 1 to 4, wherein the step-down and step-up are performed until the cooling temperature during annealing reaches 200 ° C. It is characterized by being.

That is, according to the present invention, a gas generated in the coil during annealing (hereinafter referred to as impurity gas) is discharged out of the coil by setting the inside of the annealing furnace to a negative pressure atmosphere. At this time, by repeating the pressure reduction and pressure increase in the pressure range of 0.4 × 10 ⁵ Pa to 0.9 × 10 ⁵ Pa, the impurity gas is smoothly and quickly discharged from the outside of the coil to the outside of the coil at the time of pressure reduction. A clean atmosphere gas is introduced into the furnace at the time of pressurization to prevent the foils from sticking to each other, and the impurity gas is more smoothly discharged out of the coil at the time of the pressure decrease. This prevents the occurrence of abnormalities such as variations in the oxide film and oxidation at the end of the coil due to the impurity gas not being smoothly discharged out of the coil, and it is possible to form a uniform oxide film in the width direction. Become.

In addition, when the pressure at the time of pressure reduction is regulated to 0.4 × 10 ⁵ Pa or more, when the pressure is reduced to a low pressure of less than 0.4 × 10 ⁵ Pa, the impurity gas is suddenly discharged out of the coil and the coil It is possible to avoid the occurrence of winding misalignment and adhesion between aluminum foils. On the other hand, if the pressure is excessively low, the atmospheric gas concentration is lowered, the thermal conductivity is lowered, and the annealing rate is remarkably slowed. Therefore, the thermal conductivity is secured by a pressure of 0.4 × 10 ⁵ Pa or more.
The ultimate pressure at the time of pressure reduction is preferably 0.4 × 10 ⁵ Pa or more and 0.6 × 10 ⁵ Pa or less. As a result, the impurity gas can be discharged well outside the coil, and the atmospheric gas can be quickly discharged outside the furnace. When the ultimate pressure at the time of pressure reduction is more than 0.6 × 10 ⁵ Pa, an impurity gas discharging action can be obtained, but this action is not sufficient. More preferably, the lower limit of the ultimate pressure range at the time of pressure reduction is set to 0.45 × 10 ⁵ Pa and the upper limit is set to 0.55 × 10 ⁵ Pa.

Moreover, the said impurity gas is continuously discharged | emitted out of a coil by making the pressure at the time of pressure rise into 0.9 * 10 < ⁵ > Pa or less. In addition, the cover for carrying in and out the coil provided in the annealing furnace is sufficiently adsorbed to increase the sealing performance, and the intrusion of air from the outside of the periphery of the cover is prevented. On the other hand, when the pressure is increased beyond 0.9 × 10 ⁵ Pa, the impurity gas is not sufficiently discharged, and the adsorbing force of the lid is reduced, so that the atmosphere easily enters the annealing furnace.
The ultimate pressure at the time of pressure increase is preferably 0.9 × 10 ⁵ Pa or less and preferably 0.7 × 10 ⁵ Pa or more. By setting the pressure to 0.7 × 10 ⁵ Pa or more, the atmosphere gas can be sufficiently introduced from the outside into the furnace, and adhesion of the coil during annealing can be effectively prevented. It is more desirable that the lower limit of the ultimate pressure range at the time of pressurization is 0.75 × 10 ⁵ Pa and the upper limit is 0.9 × 10 ⁵ Pa.

It should be noted that the cycle by step-down and step-up is preferably within 30 minutes per cycle. This is because gas generated from the inside of the coil is always generated, and in order to effectively remove this, it is necessary to discharge the gas and introduce a clean atmosphere. Therefore, one cycle is defined as 30 minutes or less. Above this, the prevention of contamination by the generated gas is insufficient.
Moreover, it is desirable to perform the cycle by the pressure | voltage fall and pressure | voltage rise until it falls to 200 degreeC in the cooling process at the time of annealing. This is because gas is generated from the coil up to about 200 ° C. even during the temperature drop, and it is desirable to repeat the above-described step-down and step-up in order to prevent adhesion of the foil while discharging this gas. In the state where the temperature is lower than 200 ° C., almost no gas generation is observed. In addition, since it will be end oxidation by oxygen in air | atmosphere when it takes out at a temperature more than this, it is desirable to carry out at a low temperature as much as possible.

Further, in the above annealing, until reaching 300 ° C. at the time of Atsushi Nobori, the pressure inside the furnace, without due to pressure variations due to the buck and boost pressure range of ^{0.8 × 10 5 Pa~0.9 × 10 5} Pa It is desirable to set to. This is because the rate of temperature rise is slow until the temperature reaches 300 ° C. during the temperature rise of annealing. If the pressure inside the furnace is lowered extremely to make the thermal conductivity low, the temperature rise will become even slower and the production will be slow. This is because the efficiency becomes worse. Moreover, it is desirable to set it as the pressure of 0.8 * 10 < ⁵ > Pa or more. It is desirable that the pressure in the furnace be 0.9 × 10 ⁵ Pa or less in order to obtain a gas discharge action and increase the adhesion of the furnace lid even during the temperature rise up to 300 ° C.

As described above, according to the method for producing an aluminum foil for electrolytic capacitors of the present invention, when an aluminum foil produced by cold rolling is annealed, a negative pressure atmosphere is provided and 0.4 × 10 ⁵ Pa is provided. In the pressure range of ˜0.9 × 10 ⁵ Pa, annealing is performed by repeatedly reducing the pressure by discharging the atmospheric gas and increasing the pressure by introducing the atmospheric gas, so that the aluminum foil remains in the aluminum foil coil without adhesion. Impurity gases such as oil and moisture are efficiently discharged, and a uniform oxide film can be formed in the width direction of the coil. Further, the impurity gas is not rapidly exhausted by pressure adjustment during the step-up / step-down operation, and the occurrence of coil winding deviation can be avoided. Aluminum foil with a uniform oxide film has good etching properties, and has excellent electrostatic capacity per unit area due to roughening by etching, and has a small variation in electrostatic capacity. A foil electrode can be obtained.

Below, one Embodiment of this invention is described based on FIG.
The aluminum foil used in the present invention can be preferably manufactured using an aluminum material having an aluminum purity of 99.9% or more. The aluminum material may be one to which various trace elements are added in order to improve the etching property.
In the above production, an aluminum foil having a predetermined thickness (generally 20 to 150 μm thickness) is obtained through melting, homogenization treatment (can be omitted) by casting, hot rolling, and cold rolling. Moreover, an aluminum foil may be manufactured by cold rolling after continuous casting and rolling. However, in the present invention, the composition of the aluminum material used for the aluminum foil and the manufacturing method up to annealing are not particularly limited, and the thickness of the aluminum foil is not limited to the above.

  The aluminum foil obtained after the cold rolling by the above-mentioned process is subjected to annealing that defines the production conditions in the present invention. In the annealing, an annealing furnace is used. In the present invention, the annealing furnace is not particularly limited as long as a negative pressure atmosphere can be obtained. An example of the annealing furnace 1 is shown in FIG. The annealing furnace 1 has a volume capable of accommodating an aluminum foil coil 10 wound with an aluminum foil after cold rolling, and has an opening / closing portion 2 for carrying the aluminum foil coil 10 in and out. A lid 3 for sealing the opening / closing part 2 from the outside is provided. Moreover, the annealing furnace 1 has a gas discharge / introduction section 4 that can be evacuated, discharged and introduced with atmospheric gas in a state of being sealed with the lid 3. Moreover, the annealing furnace 1 is naturally provided with heating means (not shown) for heating the aluminum foil coil 10.

In the above annealing, it is essential to set the annealing atmosphere to a negative pressure atmosphere. Further, a reducing atmosphere such as H ₂ gas or an inert gas atmosphere such as Ar or N ₂ is formed on the surface of the aluminum foil during annealing. It is desirable to adjust the thickness of the oxide film. In this atmosphere, a reducing gas and an inert gas may be mixed, or an atmosphere gas component may be changed during annealing. Further, the annealing atmosphere in the present invention is not limited to the above. The oxide film thickness is preferably 20 to 80 mm, but the oxide film thickness is not particularly limited in the present invention.

At the time of annealing, the lid 3 is opened and the aluminum foil coil 10 is carried into the annealing furnace 1 through the opening / closing part 2, and then the lid 3 is closed to seal the inside of the annealing furnace 1.
Further, before annealing, the inside of the annealing furnace is preferably evacuated to 100 Pa or less through the gas discharge / introduction section 4 to sufficiently reduce the oxygen partial pressure in the furnace. Desirably, it is more effective to perform this evacuation twice or more. After evacuation, the atmospheric gas is introduced into the annealing furnace 1 through the gas discharge / introduction section 4. When H ₂ gas is used as the atmospheric gas, it is desirable to introduce H ₂ gas after filling with an inert gas such as Ar or N ₂ after evacuation. Further, when an inert gas such as Ar or N ₂ is used as the atmosphere, the gas can be filled immediately after evacuation.

After the atmospheric gas filling is completed, annealing (heating) is started as shown in FIG. In the course of temperature increase, the temperature of the aluminum foil coil 10 and inner pressure of ^{0.8 × 10 5 Pa~0.9 × 10 5} Pa in the area to reach at least 300 ° C. is preferred. Even at the pressure in the furnace, impurity gas due to residual oil or the like is generated inside the coil and can be discharged out of the coil. In addition, because of the negative pressure atmosphere, the lid 3 is firmly adsorbed to the annealing furnace main body side, and the atmosphere enters the annealing furnace 1 from the gap between the opening and closing portion 2 and the opening and closing portion 2 and the lid 3 overlapped. Prevent intrusion.

When the temperature of the aluminum foil coil 10 becomes equal to or higher than ^{300 ℃, 0.4 × 10 5 Pa~0.9} × 10 5 in the range of Pa, preferably, the step-down of the ultimate pressure of 0.4 × ¹⁰ 5 Pa~0 in the range of .6 × ¹⁰ 5 Pa, and the ultimate pressure of the booster in the range of ^{0.7 × 10 5 Pa~0.9 × 10 5} Pa, repeating the step-up and step-down in the annealing furnace 1. The cycle in which the step-down and step-up are performed is preferably within 30 minutes.
The annealing time can be determined in consideration of the size of the coil, the annealing temperature, the progress of discharge of impurity gas generated from the coil, etc., and the present invention is limited to a specific one including the annealing temperature. However, for example, an annealing temperature of 450 to 580 ° C. and an annealing time of 2 to 24 hours can be mentioned. Further, the step-down and the step-up are not performed over the entire annealing, and may be performed during a part of the period, but preferably after heating at the annealing temperature, until the coil temperature reaches 200 ° C. upon cooling. It is desirable to continue.

The in-furnace situation at the time of step-down and step-up will be described with reference to FIG.
In annealing, impurity gas is generated by rolling oil or the like in the coil as described above by heating. This impurity gas is quickly discharged out of the aluminum foil coil 10 although it is not abrupt when the pressure in the furnace is reduced to an appropriate pressure. This impurity gas is discharged out of the annealing furnace 1 as the atmospheric gas in the annealing furnace 1 is discharged out of the annealing furnace 1 through the gas discharge / introduction section 4. When the pressure inside the furnace reaches the pressure reduction ultimate pressure and the pressure is maintained at that pressure, the discharge of the atmospheric gas and the impurity gas to the outside of the annealing furnace 1 is stopped, but the impurity gas is more gently coiled from the aluminum foil coil 10. It can be discharged outside.

Next, when the atmospheric pressure is increased to an appropriate pressure while introducing the atmospheric gas into the annealing furnace 1 through the gas discharge / introduction section 4, clean atmospheric gas diffuses into the annealing furnace 1, and the atmospheric gas The aluminum foil coil 10 is not soiled. Further, since the negative pressure is maintained at an appropriate pressure, the amount is reduced, but the impurity gas is discharged from the aluminum foil coil 10. At this time, the atmospheric pressure rises to prevent the aluminum foils in the coil from closely contacting each other. In addition, when the furnace pressure reaches the pressure increase ultimate pressure and is held at that pressure, the impurity gas is discharged from the coil until the coil pressure reaches the furnace pressure, but gas generation occurs continuously. The internal pressure exceeds the furnace pressure, the impurity gas stays in the coil, and the film is adversely affected. Therefore, in order to constantly discharge the gas in the coil and introduce the atmosphere, it is desirable to control so that the furnace pressure does not stagnate.
At the time of pressure reduction and pressure increase, the inside of the annealing furnace 1 is maintained at an appropriate negative pressure, so that the lid 3 is firmly adhered to the annealing furnace main body and maintains a good sealing property.
By repeating the above-described step-down and step-up steps, the impurity gas generated in the aluminum foil coil 10 can be quickly discharged out of the coil without incurring winding deviation or adhesion of the aluminum foil coil 10, There is no abnormality in the oxide film formed on the foil surface. As a result, an oxide film is uniformly formed on the aluminum foil even in the coil width direction.

  The aluminum foil for electrolytic capacitors obtained by the annealing is subjected to etching. The etching may be electrolytic etching or chemical etching, and a desired etching method can be employed. In the etching, a uniform oxide film is formed on the surface of the aluminum foil without any variation. Therefore, good etching is uniformly performed, and a high and uniform roughening rate is obtained. An electrolytic capacitor using the aluminum foil for electrolytic capacitors as an electrode can obtain an excellent electrostatic capacity.

In the above embodiment, the pressure change rate and the like are not described when the pressure reduction and pressure increase in the annealing furnace are repeated. In the present invention, the pressure change rate during pressure reduction and pressure increase can be set as desired. The present invention is not limited to a specific one.
FIG. 3 shows examples of pressure change patterns in the above-described step-down and step-up steps. Each pattern will be described below.

In the pattern shown in FIG. 3A, after the pressure is maintained at a predetermined negative pressure up to 300 ° C. when the temperature rises, the rapid pressure reduction and the gentle pressure increase are repeated, and the pressure change rate gradually increases in the pressure increase. So that the pressure is changed.
In the pattern shown in FIG. 3B, after maintaining a predetermined negative pressure up to 300 ° C. at the time of temperature rise, a rapid pressure drop and a pressure increase at a moderate constant change rate are repeated. The pressure is maintained for a predetermined time.
In the pattern shown in FIG. 3 (c), after maintaining a predetermined negative pressure up to 300 ° C. when the temperature is raised, the pressure is gradually lowered so that the rate of change in pressure gradually decreases, and then the rate of change in pressure gradually increases. The pressure increase is repeated, and the pressure is gradually increased when the pressure is lowered to the pressure increase, and the pressure is rapidly decreased when the pressure is lowered from the pressure increase.
In the pattern shown in FIG. 3 (d), after maintaining a predetermined negative pressure up to 300 ° C. at the time of temperature increase, the pressure is gradually decreased at a substantially constant pressure change rate, and the pressure is maintained at the ultimate pressure at the time of pressure decrease for a predetermined time. The pressure is gradually increased at a substantially constant pressure change rate, and the absolute value of the pressure change rate at the time of pressure increase is slightly larger than the absolute value of the pressure change rate at the time of pressure reduction.
Further, in the pattern shown in FIG. 3 (e), the temperature is maintained at a predetermined negative pressure up to 300 ° C. when the temperature is raised, then the pressure is rapidly decreased, the pressure is maintained at the pressure reached when the pressure is decreased for a predetermined time, and then the pressure is rapidly increased. Thus, the pressure reached at the time of pressure increase shifts to pressure decrease with little pressure holding.
Furthermore, in the pattern shown in FIG. 3 (f), after maintaining a predetermined negative pressure up to 300 ° C. when the temperature is increased, the pressure is rapidly decreased, and at the pressure reached at the time of the decrease, the pressure is shifted to a pressure increase with little pressure retention. Thus, the pressure is increased rapidly, and the pressure is held for a predetermined time at the pressure reached at the time of pressure increase.

  As mentioned above, although this invention was demonstrated based on said each embodiment, this invention is not limited to the content of the said description, A suitable change is possible in the range which does not deviate from the scope of the present invention. .

Examples of the present invention will be described below.
An aluminum slab adjusted to contain Si: 10 to 15 ppm, Fe: 10 to 15 ppm, Cu: 30 to 60 ppm, and Pb: 0.3 to 0.6 ppm using a 4N5 aluminum ingot. The obtained slab was subjected to homogenization treatment at 550 to 600 ° C. for 3 to 12 hours, and then hot rolling was started at a temperature of 500 to 600 ° C., reduction of 95 to 98% was performed, and 250 to 300 ° C. Rolled up. The hot-rolled coil was cold-rolled 98 to 99%, and then subjected to intermediate annealing at 200 to 300 ° C. for 3 to 10 hours.
10-30% of final rolling was performed after completion | finish of intermediate annealing. After rolling, cutting was performed to create a 500-550 mm wide 150 kg coil.

The obtained coil was put in an annealing furnace, and after reducing the pressure to 100 Pa or less, Ar gas or N ₂ gas was filled, and the pressure was restored to 0.9 × 10 ⁵ Pa. After returning to the original pressure, the pressure was again reduced to 100 Pa or less, filled with Ar or N ₂ gas, and returned to the annealing start furnace pressure (0.6 to 1.05 × 10 ⁵ Pa) shown in Table 1.

After setting the atmosphere to an annealing start atmospheric pressure, annealing was performed with the furnace pressure during annealing set to the pressure shown in Table 1 while supplying Ar, N ₂ gas, or H ₂ gas at 1 to 100 ml / min.
Until the coil temperature reaches 300 ° C., the atmospheric pressure is maintained in the range of 0.8 × 10 ^{5 to} 0.9 × 10 ⁵ Pa in the invention material, and in the temperature range of the coil temperature of 300 ° C. or higher, the atmospheric pressure is maintained. As shown in Table 1, annealing was performed by repeating the step-down and the step-up. In the comparative example, annealing was performed by changing the same pressure or pressure condition. In the annealing of each specimen, it is held at 500 ° C. or higher for 6 hours, and after the heating at the annealing temperature is completed, the sample is cooled at a cooling rate of 20 to 150 ° C./Hr until the coil temperature decreases to 200 ° C. Step-down and step-up were repeated. During the cooling, the pressure reduction and the atmospheric gas supply were controlled so that the atmospheric pressure shown in Table 1 could be maintained.

  When the coil temperature became 200 ° C. or less, the coil was taken out from the annealing furnace, and the winding deviation of the obtained annealing coil was inspected and the thickness of the oxide film was measured. Winding deviation is measured based on the position of the main end of the coil as a whole. The amount of outside deviation of the part that is partially outside is measured, and the outside deviation is 2 mm or less. The results were evaluated as Δ and those exceeding 5 mm as x, and are shown in Table 2. Further, the thickness of the oxide film is determined by ESCA (X-rays) at different positions in the width direction at the outer peripheral part (inner position 10 m from the outermost periphery) and the inner peripheral part (external position 15 m from the innermost periphery). The oxide film thickness was measured by photoelectron spectroscopy, and the results are shown in Table 2. The variation due to the position of the oxide film thickness was calculated as (maximum-minimum) / minimum% at a total of 6 points, 3 points on the outer periphery and 3 points on the inner periphery.

  Further, the annealing coil was rewound, and the adhesiveness of the foil was evaluated based on the degree of wrinkle generation. At that time, the evaluation was made as “No” wrinkle, “△” for the longest wrinkle length of 50 cm or less, and “×” for the longest wrinkle length of more than 50 cm. Further, the degree of discoloration of the end face was observed, and the case where discoloration could be confirmed with a width of 10 mm or more from the end portion was evaluated. These results are also shown in Table 2.

It is a figure explaining the structure of the annealing furnace used for one Embodiment of this invention, and the gas flow at the time of pressure | voltage fall and pressure | voltage rise. Similarly, it is a figure which shows the temperature pattern and pressure pattern at the time of annealing. It is a figure (af) which shows each pressure pattern at the time of annealing in other embodiment of this invention.

Explanation of symbols

1 Annealing furnace 2 Opening / closing part 3 Lid 4 Gas exhaust / introduction part

Claims (5)

When annealing the aluminum foil produced by cold rolling, with a negative pressure atmosphere in the pressure range of ^{0.4 × 10 5 Pa~0.9 × 10 5} Pa, the step-down by the discharge of atmospheric gases and atmosphere A method for producing an aluminum foil for an electrolytic capacitor, characterized in that annealing is repeated by increasing the pressure by introducing gas. The ultimate pressure of the step-down is in the range of ^{0.4 × 10 5 Pa~0.6 × 10 5} Pa, the ultimate pressure of the booster is ^{0.7 × 10 5 Pa~0.9 × 10 5} Pa The method for producing an aluminum foil for an electrolytic capacitor according to claim 1, wherein the method is set within a range.   The method for producing an aluminum foil for an electrolytic capacitor according to claim 1 or 2, wherein one cycle in which the step-down and the step-up are performed is within 30 minutes. When to annealing at annealing temperature was raised to the aluminum foil, in the middle heated to the aluminum foil does not reach 300 ° C. sets the ambient pressure to ^{0.8 × 10 5 Pa~0.9 × 10 5} Pa The manufacturing method of the aluminum foil for electrolytic capacitors in any one of Claims 1-3 characterized by the above-mentioned.   The method for producing an aluminum foil for an electrolytic capacitor according to any one of claims 1 to 4, wherein the step-down and the step-up are performed until the cooling temperature during annealing reaches 200 ° C.

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